U.S. Pat. No. 3,837,783 describes a die for extruding bodies of cellular structure (in particular bodies made of ceramic materials). The design of that die is monolithic and includes feed ducts made through a solid member, the downstream ends of said ducts communicating with a network of interconnected discharge slots organized in a grating configuration with the extruded material emerging directly via said slots; since the ducts are longitudinal, it is necessary to impede the longitudinal flow of the material to promote lateral flow of part thereof so as to cause the material extruded from different ducts to join together, this makes it possible to form directly the various cellular structures defining walls of the body.
A die of that type is not suitable when it is required to extrude bodies of large cross-section, e.g. a cylindrical structure 200 mm in diameter. Indeed, the part which has holes at many locations to define the ducts must necessarily be very thick for it to have sufficient mechanical strength to withstand high feed pressures. This makes it necessary to provide holes which are very long with respect to their bores and the length-to-bore ratio then greatly exceeds 10 which is generally considered unfavourable. This is a great but inevitable limitation when using present techniques based on this principle.
The invention aims to improve the design of conventional monolithic tooling by providing a strong die which is suitable for extruding bodies of large cross-section but which remains easy to produce using ordinary machining techniques.